1. Field of the Invention
The present invention relates to a method of manufacturing liquid crystal display panels (LCD panels) in which a multiplicity of liquid crystal display panels are cut and manufactured from a single glass substrate (mother glass) on a gang printing basis.
2. Description of the Related Art
FIG. 13 shows a flow of steps for manufacturing liquid crystal display panels according to the related art utilizing a vacuum injection process. Among the steps for manufacturing liquid crystal display panel, the vacuum injection process is used for sealing a liquid crystal between two glass substrates facing each other by combining the two glass substrates having pixel electrodes, or a common electrode and various lines formed thereon with a predetermined gap left therebetween and injecting the liquid crystal in the gap through an opening provided at a combined end section in a vacuum atmosphere.
In the case of multi-shot in which a plurality of LCD panels is cut from a single glass substrate, as shown in FIG. 13, a substrate to serve as TFT substrates having a plurality of TFT substrate regions formed thereon is first combined with a substrate to serve as CF substrates having a plurality of CF substrate regions formed in association with the TFT substrate regions. Next, the combined substrates are broken along predetermined scribe lines to be cut into individual liquid crystal display panels into which a liquid crystal is injected utilizing capillarity in a vacuum chamber.
Recent techniques for manufacturing LCD panels that have been put in use include a dispenser injection process in which a liquid crystal is dispensed on each of TFT substrate regions on a gang-printed glass substrate (e.g., a substrate to serve as TFT substrates) and in which the substrate is then combined with a substrate to serve as CF substrates to seal the liquid crystal. FIG. 14 shows a flow of steps for manufacturing liquid crystal display panels according to the related art utilizing the dispenser injection process. Pillar spacers for maintaining a cell gap are formed in each of TFT substrate regions on a gang-printed substrate to serve as TFT substrates. A rubbing process is performed when needed after printing an alignment film. Then, a liquid crystal is dispensed in each of the TFT substrate regions while controlling the quantity of the droplet.
Each of CF substrate regions on a gang-printed substrate to serve as CF substrates is subjected to a rubbing process when needed after printing an alignment film on the same, and a sealing material that is set when irradiated with ultraviolet (UV) rays is applied around each of the CF substrate regions. The substrate to serve as CF substrates is laid on the substrate to serve as TFT substrates in alignment with the same, and the two mother glasses are combined by irradiating the sealing material with ultraviolet rays to set the same. Thus, the dispenser injection process is advantageous in that panels can be fabricated in a very short time compared to the vacuum injection process in which a long time is required for sealing a liquid crystal. The dispenser injection process completes the injection of a liquid crystal on mother glasses unlike the vacuum injection process in which a liquid crystal is injected after individual liquid crystal display panels are cut from mother glasses.
Some of steps for forming liquid crystal display panel cells involve an operation of applying a voltage after a liquid crystal is injected. FIGS. 13 and 14 indicate such steps involving the application of a voltage with hatching.
An operation of applying a voltage that is normally performed after the injection of a liquid crystal is a panel test step in which each cell is judged good or not by turning it on before a module step at which driver ICs are mounted using TAB (tape-automated bonding). In the case of gang printing in which a plurality of panel layouts can be provided on a mother glass, an inspection of display defects of each liquid crystal display panel is performed by separately applying a predetermined voltage to each liquid crystal display panel to inspect whether the pixels are properly turned on and off after cutting each liquid crystal display panel from the mother glass.
In addition to the above-described inspection of display defects, there are two processes at which a voltage is applied to a liquid crystal display panel as described below. The first process is performed when using a method of stabilizing alignment of a liquid crystal in which a liquid crystal material including a monomer is used and in which the monomer is polymerized to stabilize the alignment of the liquid crystal. According to the method of stabilizing alignment of a liquid crystal using a polymer, for example, a vertically aligned liquid crystal (VA liquid crystal) having negative dielectric constant anisotropy is added with a monomer that is polymerized by irradiating the same with ultraviolet rays. Next, the monomer is polymerized by irradiating the same with ultraviolet rays while applying a predetermined voltage to the liquid crystal after sealing the liquid crystal between two substrates. A pretilt angle of the liquid crystal is controlled by the polymer. The pretilt angle of the liquid crystal depends on the magnitude of the voltage applied to the liquid crystal, for example.
The other process involving application of a voltage is performed when a ferroelectric liquid crystal is used. A voltage must be applied to a ferroelectric liquid crystal while it is heated in order to achieve uniform orientation of alignment. When a liquid crystal material exhibiting a series of phase transitions expressed by ISO→N*→SmC*, a domain having inverted spontaneous polarization is normally formed in the SmC* phase. While uniform alignment cannot be achieved throughout the liquid crystal because of the domain, uniform alignment can be achieved by applying a DC bias to the liquid crystal in the vicinity of the N* → SmC* transition. Therefore, when a ferroelectric liquid crystal is sealed between substrates, there must be a process at which a voltage is applied with the temperature of the liquid crystal increased to the point of the phase transition.
At those voltage applying processes, a terminal section for applying a voltage to an LCD panel must be exposed. Therefore, in the case of gang printing in which a plurality of panel regions are provided on a mother glass, the mother glass is cut into individual liquid crystal display panels to which a voltage is applied separately.
In the case of a gang-printed product, the number of panels obtained from a single mother glass can range from several pieces to several tens pieces or more. Therefore, when an operation of applying a voltage to individual liquid crystal display panels is performed after cutting the individual liquid crystal display panels from a mother glass as shown in FIGS. 13 and 14, an operation of transporting the multiplicity of liquid crystal display panels to and from an inspection apparatus becomes complicated. Thus, the voltage applying process takes a long time to result in the problem of an increase in the manufacturing cost. Further, since the voltage applying operation itself increases the number of manufacturing steps, it can reduce production efficiency.